Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session J5: Undergraduate Session |
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Chair: Wesley Walter, Denison University Room: Clark Hall 107 |
Thursday, May 21, 2009 8:00AM - 8:20AM |
J5.00001: Light Polarization Dependence of Optical Dipole Traps Created in the Diffraction Pattern of a Pinhole Invited Speaker: We will present the results of our computational exploration of the atom trapping potentials in the diffraction pattern that forms behind, but very close to a small pinhole [1]. Specifically we explored the polarization dependence of these traps [2]. Our simulation indicates it is possible to create two distinct optical dipole traps for atoms in the F = 1 and m$_{F}$ $_{ }$= +1,-1 sub-states using $\sigma ^{+}$ and $\sigma ^{-}$ polarized light. We explored a range of incident laser angles and found that by adjusting the angles it is possible to manipulate the physical location of atoms that are in the dipole traps. The traps stayed intact beyond angles of 6\r{ }, at which point the traps are completely separated. For a 25 $\mu $m pinhole and $\sim $100 mW of laser light, tuned 1000 linewidths to the blue of the D2 transition in Rubidium 87 we found trap depths of $\sim $1 mK, radial trap frequencies of $\sim $10 kHz and axial trap frequencies of several kHz. The main goal of this study was to explore a method through which we could create a controllable optical dipole trap that may allow for the implementation of 2-qubit gates using two-dimensional arrays of optical dipole traps.\\[4pt] [1] G. D. Gillen, et al., Phys. Rev. A 73 (2006), 013409\\[0pt] [2] I.Deutsch, et al., Phys. Rev. A, 57 (3), 1972-1986 (1998). [Preview Abstract] |
Thursday, May 21, 2009 8:20AM - 8:40AM |
J5.00002: Semi-classical electron dynamics and the generation of below threshold harmonics Invited Speaker: We study the generation of below threshold harmonics in a model atom. We extend the three-step semi-classical model of high harmonic generation (HHG) to include effects of the atomic potential which necessarily plays an important role. We explore the generalization of semi-classical trajectories in the presence of the potential. We show that the long trajectory readily generalizes to below threshold HG. We also discuss that this is in good agreement with fully quantum mechanical calculations as well as with recent experimental results. [Preview Abstract] |
Thursday, May 21, 2009 8:40AM - 9:00AM |
J5.00003: Polarizability Measurements in a Multi-Species Atom Interferometer Invited Speaker: We have measured the polarizability of Na, K, and Rb atoms by applying an electric field gradient in an atom interferometer. We measured the DC ground state polarizability of Na atoms with a precision of 1{\%}, and we are working on similar precision for direct measurements with K and Rb atoms. By using nanofabricated gratings, we have observed diffraction and interference fringes for several different types of atoms in the same apparatus. We can use the same electric field region, the same collimating slits, and same detector for each atomic species. With this approach, some systematic uncertainties in the measurement of atomic polarizability are the same for every atomic species. We therefore anticipate reporting ratio measurements of polarizabilities with precision better than 1{\%}. [Preview Abstract] |
Thursday, May 21, 2009 9:00AM - 9:20AM |
J5.00004: Modeling BEC's in Double Wells Invited Speaker: We introduce a new method for the simulation of Bose-Einstein condensates in regimes where both mean field effects (Gross-Pitaevskii theory) and the fragmentation of states (Bose-Hubbard model) play significant roles. This procedure takes advantage of the differing time scales of spatial wave-function deformation and changes in Fock-space expansion coefficients via use of a novel basis. These 2,3D simulations are used to analyze two often cited experiments [1,2]. An experiment from the MIT cold atom group [1] is shown to reach tentative conclusions, not fully consistent with the present simulations. Namely, full fragmentation is not achieved. The time scale used for raising the potential barrier is also seen to result in substantial non-adiabaticity. This confuses analysis of number squeezing, as both result in degradation of interference patterns. Results of an experiment from the Heidelberg group [2], including both Josephson and self trapped dynamics, are modeled and extended to number entangled states.\\[4pt] [1] Y. Shin et al., PRL \textbf{93}, 050405 (2004)\\[0pt] [2] M. Albiez et al., PRL \textbf{95}, 010402 (2005). [Preview Abstract] |
Thursday, May 21, 2009 9:20AM - 9:40AM |
J5.00005: Molecular analogs for studying the time-dependence of atomic ionization Invited Speaker: Many groups around the world are trying to use attosecond laser pulses to study the time-dependence of electron motion in atoms and molecules. We propose an alternative method that is capable of revealing insight into this motion without the need for attosecond pulses. Specifically, we have used the process of above threshold dissociation (ATD) of HeH$^{+ }$as an analog to the atomic phenomenon of above threshold ionization (ATI). This analogy is verified by calculations made for the kinetic energy release spectrum for ATD that show the spectrum to contain several clear peaks, like the photoelectron spectrum for ATI. The laser parameter regime of ten-cycle pulses with intensities of 10$^{14}$ W/cm$^{2}$ and a range of wavelengths from 2000 to 2400 nm has been shown to produce experimentally detectable dissociation probabilities for HeH$^{+}$. Since the ATD of HeH$^{+ }$produces fragments, HeH$^{+ }$+ \textit{nh$\nu $}$\to ^{ }$He(1$s^{2})$ + H$^{+}$ , that are much more massive than an ionized electron, current pump-probe techniques can be used to experimentally verify predictions for the time-dependence of the nuclear motion in ATD for this laser parameter regime. By analogy, this allows experimental verification of predictions for electron motion in ATI. [Preview Abstract] |
Thursday, May 21, 2009 9:40AM - 10:00AM |
J5.00006: Ionization of Methane in Strong and Ultrastrong Fields Invited Speaker: The photoionization of methane is reported for intensities up to 10$^{19}$ W/cm$^{2}$ with linear and circular polarized light. While fragmental ions (e.g. CH$_{3}^{+}$, CH$^{+}$, C$^{+}$, C$^{+2})$ created from 10$^{14}$ W/cm$^{2}$ to 10$^{15}$ W/cm$^{2}$ are formed by Coulomb explosion, ionization to form C$^{+3}$ and C$^{+4}$ involves Coulomb explosion and tunneling ionization. In ultrastrong fields, removal of a carbon K-shell electron from methane proceeds via tunneling and rescattering ionization, without the influence of molecular channels. Photoelectrons from methane at 10$^{19}$ W/cm$^{2}$ extend up to kinetic energies of 0.6 MeV. [Preview Abstract] |
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